Moldings of thermoplastic resins such as acrylic resin generally have gloss (luster), and the gloss is an important property for some uses. On the other hand, there are also many uses that do not require gloss or prefer to be not glossy. In particular, matt moldings are preferred for uses such as interior materials for vehicles, furniture, housing of electric equipment, wallpapers and building materials.
Conventional processes for matting thermoplastic resins are roughly classified into (1) a process by embossing or by mechanical or chemical matting processing, and (2) a process by addition of an inorganic or organic matting agent.
The process (1) has the advantage that in general decrease in physical properties is small, but has the problems that in addition to low productivity and increase in processing cost, the matting effect is not sufficient and, in many cases, gloss is restored if films are heated in secondary processing, thus the matting effect is lost. On the other hand, the process (2) has the advantages that the productivity does not decrease so much, it is easy to control the matting degree and the products are also applicable to uses wherein the products are subjected to secondary processing, but has a large problem of decrease in physical properties. In particular, in case of using an inorganic material such as silica gel as a matting agent, decrease in physical properties such as impact resistance, tensile strength, elongation and transparency is marked.
Also, in case of making a print on the surface of acrylic resin films, the process (2) has the problem that printing defect may occur due to protrusions (hereinafter referred to as “fish eye”) on the surface resulting from foreign matter. With regard to transparent films, it is known for solving the printing defect problem to bring the both surfaces of a film to contact with rolls kept at a temperature higher than Tg of the film. However, this method has the problem for matt films that the matt surface gets back to gloss surface. In JP-A-03-237134 is proposed a method by incorporation of an organic matting agent, but in case of making a print onto films, this method has the problems that since unevenness of the film surface is large, ink is hard to transfer onto concave portions, so no sharp printed pattern is obtained, or printing defect takes place at protrusions on the film surface.
It is an object of the present invention to solve the above-mentioned problems and to provide a matt acrylic thermoplastic resin film, without impairing physical properties such as matting property, impact resistance, heat resistance, tensile strength and elongation, which is improved so as to prevent the printing defect from occurring as much as possible by decreasing protrusions on the film surface, and is improved, besides improvement in ink receptivity, so as to maintain a low glossiness of one surface, and further which is hard to get back to gloss surface even if subjected to secondary processing.